JPH10245668A - Method for nitriding ferrous material and ferrous material product obtained thereby - Google Patents
Method for nitriding ferrous material and ferrous material product obtained therebyInfo
- Publication number
- JPH10245668A JPH10245668A JP6737897A JP6737897A JPH10245668A JP H10245668 A JPH10245668 A JP H10245668A JP 6737897 A JP6737897 A JP 6737897A JP 6737897 A JP6737897 A JP 6737897A JP H10245668 A JPH10245668 A JP H10245668A
- Authority
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- Japan
- Prior art keywords
- iron
- nitriding
- based material
- nitride layer
- treatment
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、鉄系材料の窒化処
理方法およびそれによって得られた鉄系材料製品に関す
るものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for nitriding an iron-based material and an iron-based material product obtained by the method.
【０００２】[0002]
【従来の技術】一般に、エアコンやクーラー等のコンプ
レッサー用の各種摺動部材としては、鋳鉄や炭素鋼が使
用されている。そして、耐摩耗性向上策として、浸炭焼
き入れ，高周波焼き入れ等の焼き入れ硬化や、ＰＶＤ
（ｐｈｙｓｉｃａｌ ｖａｐｏｒｄｅｐｏｓｉｔｉｏ
ｎ）等の乾式めっきを施すことが行われてきた。2. Description of the Related Art Generally, cast iron and carbon steel are used as various sliding members for compressors such as air conditioners and coolers. As measures to improve wear resistance, quenching and hardening such as carburizing and induction hardening, and PVD
(Physical vapordepositio
n) and the like.
【０００３】上記焼き入れ硬化法では、鋼の変態点（鋼
がオーステナイト相となるＡ3 もしくはＡcm変態点）を
越える高温からの急冷が必要であることから、処理前後
の寸法変化や歪みの発生が大きい。このため、最終製品
の研削仕上げ等が必要になり、仕上げ加工に多大なコス
トがかかるという問題がある。一方、乾式めっき法で
は、母材とコーティング層の密着性に難があるうえ、量
産性が悪く、処理コストが高いという問題がある。[0003] In the above quenching curing method, transformation point of steel since it is necessary rapid cooling from the high temperature exceeding (steel A 3 or A cm transformation point becomes an austenite phase), before and after the treatment dimensional change or distortion of Outbreak is large. For this reason, there is a problem in that the final product needs to be ground and finished, and the finishing process requires a large cost. On the other hand, the dry plating method has problems in that the adhesion between the base material and the coating layer is difficult, the mass productivity is low, and the processing cost is high.
【０００４】したがって、最近では、鉄系材料の表面硬
化法として、比較的低温で処理することができ、寸法変
化や歪みが比較的少ない窒化処理法が採用される傾向に
ある。Accordingly, recently, as a method of hardening the surface of an iron-based material, a nitriding method, which can be treated at a relatively low temperature and has a relatively small dimensional change and distortion, has been used.
【０００５】[0005]
【発明が解決しようとする課題】ところが、窒化処理で
あっても、５４０〜５８０℃の温度下で長時間加熱され
るため、残留応力の解放や鋼の再結晶等が起こることに
よる熱変形が避けられない。また、鋼を窒化処理する
と、最表面に窒化物層が形成され、その下層に、窒素が
拡散浸透するとともに微細窒化物が分散した拡散層が形
成される。これらは、寸法の膨れや面粗度，真円度の悪
下等の精度低下の原因となっている。一方、装置の高回
転化に伴う製品の高精度化の要求はますます厳しくな
り、窒化処理品であっても、焼き入れ品と同様に研削仕
上げ等の仕上げ加工が必要になっているのが実情であ
る。However, even in the case of nitriding, since heating is carried out at a temperature of 540 to 580 ° C. for a long time, thermal deformation due to release of residual stress or recrystallization of steel occurs. Inevitable. Further, when the steel is nitrided, a nitride layer is formed on the outermost surface, and a diffusion layer in which nitrogen diffuses and penetrates and fine nitride is dispersed is formed below the nitride layer. These are causes of a decrease in accuracy such as dimensional swelling, surface roughness, and poor roundness. On the other hand, the demand for higher precision of products accompanying higher rotational speeds of equipment has become more and more severe, and even for nitrided products, finish processing such as grinding finish is required like hardened products. It is a fact.
【０００６】また、鋼の再結晶等による熱変形を小さく
しようとして、再結晶温度（鉄の再結晶温度は、約４５
０℃）以下の低温で窒化処理を行うと、窒素の拡散浸透
が充分行われずに、窒化硬化層の形成が著しく不安定に
なるという問題が生じる。特に、切削，研削等の機械加
工を行った部材では、表面に生じた加工変質層の影響
で、さらに窒化硬化層の形成が不安定になりやすい。こ
のため、従来、上記のような低温でガス窒化処理が行わ
れることはなかった。[0006] Further, in order to reduce thermal deformation due to steel recrystallization or the like, the recrystallization temperature (iron recrystallization temperature is about 45
If the nitriding treatment is performed at a low temperature of 0 ° C. or less, there is a problem that the diffusion and infiltration of nitrogen is not sufficiently performed and the formation of the nitrided hardened layer becomes extremely unstable. In particular, in a member that has been subjected to mechanical processing such as cutting and grinding, the formation of a nitrided hardened layer is likely to be further unstable due to the influence of a work-affected layer generated on the surface. For this reason, conventionally, gas nitriding has not been performed at such a low temperature.
【０００７】本発明は、このような事情に鑑みなされた
もので、処理前後の寸法変化や歪みが少なく、寸法精
度，面粗度等に優れた製品が得られる鉄系材料の窒化処
理方法およびそれによって得られた鉄系材料製品の提供
をその目的とする。The present invention has been made in view of such circumstances, and a method of nitriding an iron-based material, which has a small dimensional change and distortion before and after processing, and has excellent dimensional accuracy, surface roughness, and the like, is provided. The aim is to provide iron-based material products obtained thereby.
【０００８】[0008]
【課題を解決するための手段】上記の目的を達成するた
め、本発明の鉄系材料の窒化処理方法は、窒化処理に先
立って、フッ素系ガス雰囲気下で鉄系材料を加熱保持し
てフッ化処理し、ついで、窒化処理の際の温度を３００
〜４５０℃に設定し、上記フッ化処理済の鉄系材料を窒
化処理することにより、上記フッ化処理済の鉄系材料の
表層部の少なくとも一部に、厚み１〜１０μｍの窒化物
層を形成することを要旨とする。In order to achieve the above object, the present invention provides a method for nitriding an iron-based material, which comprises heating and holding the iron-based material in a fluorine-based gas atmosphere prior to nitriding. And then the temperature at the time of nitriding is set to 300
By setting the temperature to ~ 450 ° C and nitriding the fluorinated iron-based material, a nitride layer having a thickness of 1 to 10 µm is formed on at least a part of the surface layer of the fluorinated iron-based material. The point is to form.
【０００９】また、本発明の鉄系材料製品は、母材が鉄
系材料からなり、表層部の少なくとも一部に、厚み１〜
１０μｍの窒化物層が形成されていることを要旨とす
る。Further, in the iron-based material product of the present invention, the base material is made of an iron-based material, and at least a part of the surface layer has a thickness of 1 to 3.
The gist is that a nitride layer of 10 μm is formed.
【００１０】本発明者らは、窒化処理方法において処理
前後の寸法変化や歪みを少なくするため、一連の研究を
重ねた。そして、窒化処理に先立って、フッ素系ガス雰
囲気下で鉄系材料を加熱保持してフッ化処理することに
より、鉄系材料の表面が活性化され、窒化されやすくな
るという知見を得た。そして、種々実験を繰り返した結
果、フッ化処理することにより、従来不可能と思われて
いた３００〜４５０℃の低温域での窒化が可能になり、
さらに、上記低温域での窒化処理により表層部の少なく
とも一部に、厚み１〜１０μｍの窒化物層を形成するこ
とにより、処理前後の寸法変化や歪みが極めて少なくな
り、寸法精度，面粗度等に優れた製品が得られることを
突き止め、本発明に到達した。The present inventors have conducted a series of studies in order to reduce dimensional changes and distortions before and after the nitriding process. Further, it has been found that prior to the nitriding treatment, the surface of the iron-based material is activated and easily nitrided by heating and holding the iron-based material in a fluorine-based gas atmosphere to perform the fluorination treatment. And, as a result of repeating various experiments, nitriding in a low temperature range of 300 to 450 ° C., which was considered impossible in the past, becomes possible by performing fluorination treatment.
Furthermore, by forming a nitride layer having a thickness of 1 to 10 μm on at least a part of the surface layer portion by the nitriding treatment in the low temperature range, dimensional change and distortion before and after the treatment are extremely reduced, and dimensional accuracy and surface roughness are reduced. As a result, it has been found that a product having excellent properties is obtained, and the present invention has been achieved.
【００１１】[0011]
【発明の実施の形態】つぎに、本発明の実施の形態を説
明する。Next, an embodiment of the present invention will be described.
【００１２】本発明の窒化処理方法は、窒化処理に先立
って、フッ素系ガス雰囲気下で鉄系材料を加熱保持し、
ついで、窒化処理の際の温度を３００〜４５０℃に設定
して窒化処理することにより、表層部の少なくとも一部
に、厚み１〜１０μｍの窒化物層を形成する。In the nitriding method of the present invention, prior to the nitriding treatment, the iron-based material is heated and held in a fluorine-based gas atmosphere,
Next, a nitride layer having a thickness of 1 to 10 μm is formed on at least a part of the surface layer by performing a nitridation process at a temperature of 300 to 450 ° C. during the nitriding process.
【００１３】上記鉄系材料としては、特に限定するもの
ではなく、各種のものが用いられる。例えば、窒化鋼、
ニッケル・クロム鋼，ニッケル・クロム・モリブデン
鋼，クロム鋼，クロム・モリブデン鋼等の機械構造用炭
素鋼、マンガン・クロム鋼，クロム・バナジウム鋼，珪
素・マンガン鋼等のばね鋼、高炭素クロム鋼，タングス
テン・クロム鋼，タングステン・バナジウム鋼等の工具
鋼、タングステン・クロム・バナジウム鋼等の高速度鋼
の他、マンガン鋼，Ｈ鋼，高張力鋼，快削鋼，ダイス
鋼，軸受鋼，耐熱鋼，ボロン鋼等の各種合金鋼や、ねず
み鋳鉄，白鋳鉄，まだら鋳鉄，フェライト鋳鉄，パーラ
イト鋳鉄，球状黒鉛鋳鉄，接種鋳鉄，可鍛鋳鉄等の各種
鋳鉄、鋳鋼等があげられる。また、鋼だけでなく、炭素
をほとんど含有しない工業用純鉄でもよいし、この純鉄
や炭素鋼等に浸炭処理を行ったものでもよい。さらに、
溶製鋼に限らず、粉末冶金法によって得られる焼結合金
でもよい。これらの鉄系金属は、あらかじめ調質，応力
除去焼鈍等の熱処理を行ってもよい。The iron-based material is not particularly limited, and various materials can be used. For example, nitrided steel,
Nickel-chromium steel, nickel-chromium-molybdenum steel, chrome steel, chromium-molybdenum steel, etc., carbon steel for mechanical structures, manganese-chromium steel, chromium-vanadium steel, spring steel such as silicon-manganese steel, high-carbon chromium steel , Tungsten-chromium steel, tool steel such as tungsten-vanadium steel, high-speed steel such as tungsten-chromium-vanadium steel, manganese steel, H steel, high-strength steel, free-cutting steel, die steel, bearing steel, heat-resistant Examples include various alloy steels such as steel and boron steel, various cast irons such as gray cast iron, white cast iron, mottled cast iron, ferrite cast iron, pearlite cast iron, spheroidal graphite cast iron, inoculated cast iron, and malleable cast iron, and cast steel. Further, not only steel but also industrial pure iron containing almost no carbon may be used, or pure iron or carbon steel may be subjected to carburizing treatment. further,
Not limited to ingot steel, but a sintered alloy obtained by powder metallurgy may be used. These iron-based metals may be subjected to heat treatment such as tempering and stress relief annealing in advance.
【００１４】上記鉄系材料を、窒化処理に先立って、ま
ず、フッ素系ガス雰囲気下で加熱保持してフッ化処理す
る。Prior to nitriding, the iron-based material is first subjected to fluorination by heating and holding it in a fluorine-based gas atmosphere.
【００１５】上記フッ化処理に用いるフッ素系ガスとし
ては、ＮＦ3 ，ＢＦ3 ，ＣＦ4 ，ＨＦ，ＳＦ6 ，Ｃ2 Ｆ
6 , ＷＦ6 ，ＣＨＦ3 ，ＳｉＦ等からなるフッ素化合物
ガスおよびＦ2 ガスがあげられ、単独でもしくは併せて
使用される。また、これら以外に分子内にフッ素を含む
他のフッ素化合物ガスもフッ素系ガスとして用いること
ができる。このようなフッ素系ガスは、それのみで用い
ることもできるが、通常は、Ｎ2 ガス等の不活性ガスで
希釈されて使用される。このような希釈されたガスにお
けるフッ素系ガスの濃度は、例えば１００００〜１００
０００ｐｐｍであり、好ましくは２００００〜７０００
０ｐｐｍ、より好ましくは、３００００〜５００００ｐ
ｐｍである。この種のフッ素系ガスとして最も実用性を
備えているのはＮＦ3 である。ＮＦ3 は常温でガス状で
あり化学的安定性が高く取り扱い性が容易だからであ
る。As the fluorine-based gas used for the fluorination treatment, NF 3 , BF 3 , CF 4 , HF, SF 6 , C 2 F
6, WF 6 , CHF 3 , SiF and other fluorine compound gas and F 2 gas, which may be used alone or in combination. In addition, other fluorine compound gases containing fluorine in the molecule can also be used as the fluorine-based gas. Such a fluorine-based gas can be used alone, but is usually used after being diluted with an inert gas such as N 2 gas. The concentration of the fluorine-based gas in such a diluted gas is, for example, 10,000 to 100
2,000 ppm, preferably 20,000-7000
0 ppm, more preferably 30,000 to 50,000p
pm. NF 3 is the most practical as this kind of fluorine-based gas. This is because NF 3 is gaseous at room temperature, has high chemical stability, and is easy to handle.
【００１６】フッ化処理は、上記濃度のフッ素系ガス雰
囲気を作り、この雰囲気下に、上記鉄系材料を入れ加熱
状態で保持することにより行う。この場合の加熱温度
は、例えば、２５０〜４５０℃の温度に設定される。そ
して、加熱保持時間は、製品の種類や形状寸法，加熱温
度等に応じて適当な時間を設定すればよく、通常は、十
数分〜数十分の範囲内に設定される。鉄系材料をフッ化
処理することにより、「Ｎ」原子が鉄系材料の表面から
内部に浸透しやすくなる。この理由は、鉄系材料の表面
には、ＦｅＯ，Ｆｅ3 Ｏ4 ，Ｃｒ2 Ｏ3 等の酸化物皮膜
等が形成されているが、この酸化物皮膜等が形成された
鉄系材料を上記のようにフッ化処理すると、上記酸化物
がフッ素系ガスと反応し、ＦｅＦ2 ，ＦｅＦ3 ，ＣｒＦ
2 ，ＣｒＦ4 等の化合物を含む薄いフッ化膜に変換され
て活性化し、窒化ガス中の「Ｎ」原子の浸透が容易な表
面状態になると考えられる。このように、鉄系材料の表
面が「Ｎ」原子の浸透が容易な状態になっているため、
４５０℃以下の比較的低温域でも「Ｎ」原子が一定の深
さで均一に拡散し、均一な窒化層が形成されると考えら
れる。The fluorination treatment is carried out by creating a fluorine-based gas atmosphere having the above concentration, placing the iron-based material in this atmosphere, and keeping the iron-based material in a heated state. The heating temperature in this case is set to, for example, a temperature of 250 to 450 ° C. The heating holding time may be set to an appropriate time according to the type, shape and size of the product, the heating temperature, and the like, and is usually set in the range of ten minutes to several tens of minutes. By fluorinating the iron-based material, “N” atoms can easily penetrate from the surface of the iron-based material to the inside. The reason is that an oxide film such as FeO, Fe 3 O 4 , Cr 2 O 3 or the like is formed on the surface of the iron-based material. When the fluorination treatment is performed as described above, the above oxide reacts with the fluorine-based gas to produce FeF 2 , FeF 3 , CrF
It is considered that the surface is converted into a thin fluorinated film containing a compound such as 2 , CrF 4 and activated, and becomes a surface state in which “N” atoms in the nitriding gas easily penetrate. As described above, since the surface of the iron-based material is in a state where "N" atoms can easily penetrate,
It is considered that even in a relatively low temperature range of 450 ° C. or lower, “N” atoms diffuse uniformly at a constant depth, and a uniform nitride layer is formed.
【００１７】ついで、上記のように、フッ化処理によっ
て「Ｎ」原子の浸透し易い状態となっている鉄系材料を
窒化雰囲気下において加熱状態で保持し、窒化処理が行
われる。Next, as described above, the iron-based material which is in a state where "N" atoms easily penetrate by the fluoridation treatment is held in a heating state in a nitriding atmosphere, and the nitriding treatment is performed.
【００１８】この場合、窒化雰囲気をつくる窒化ガスと
しては、ＮＨ3 のみからなる単体ガス、または、上記単
体ガスにＮ2 等の不活性ガスを混合して使用される。場
合によっては、これらのガスにＨ2 ガスを混合して使用
することも行われる。In this case, as the nitriding gas for creating the nitriding atmosphere, a simple gas consisting of only NH 3 or a mixture of the above simple gas with an inert gas such as N 2 is used. In some cases, these gases may be mixed with H 2 gas for use.
【００１９】上記窒化雰囲気下において、フッ化処理の
なされた鉄系材料が加熱状態で保持される。この場合の
加熱温度は、従来の窒化処理よりも大幅に低い温度の３
００〜４５０℃に設定される。すなわち、上記温度が４
５０℃を越えると、鉄系材料の再結晶等が起こり熱変形
等が生じるが、４５０℃以下で処理することにより、再
結晶等に起因する熱変形が抑えられる。また、上記窒化
処理時間は、通常２〜４８時間に設定される。なお、３
００℃以下の窒化処理温度では、長時間窒化処理しても
充分な厚みの窒化硬化層が得られないため、実用的では
ない。In the nitriding atmosphere, the fluorinated iron-based material is kept in a heated state. The heating temperature in this case is 3 which is much lower than the conventional nitriding treatment.
It is set at 00-450 ° C. That is, when the temperature is 4
If the temperature exceeds 50 ° C., recrystallization or the like of the iron-based material occurs and thermal deformation or the like occurs. However, by performing the treatment at 450 ° C. or less, the thermal deformation due to the recrystallization or the like is suppressed. The nitriding time is usually set to 2 to 48 hours. In addition, 3
At a nitriding temperature of 00 ° C. or lower, it is not practical because a nitrided hardened layer having a sufficient thickness cannot be obtained even if the nitriding is performed for a long time.
【００２０】上記のようなフッ化処理および窒化処理
は、例えば、図１に示すような金属製のマッフル炉１で
行われる。このマッフル炉１は、ヒータ３によって加熱
される内容器４と、この内容器４を収容する外殻２を備
えている。そして、上記内容器４には、雰囲気ガスを導
入するガス導入管５および排気管６が連通している。上
記ガス導入管５には、流量計１７およびバルブ１８を介
してフッ素系ガスボンベ１６，ＮＨ3 ガスボンベ１５，
Ｎ2 ガスボンベ３０が接続されている。一方、上記排気
管６には、内容器４内のガスを排気する真空ポンプ１３
および排ガス処理装置１４が接続されている。図におい
て、８はモーター７で回転して内容器４内の雰囲気ガス
を攪拌するファンであり、１１は鉄系材料１０を詰める
金網製かごである。The above fluorination treatment and nitridation treatment are performed, for example, in a metal muffle furnace 1 as shown in FIG. The muffle furnace 1 includes an inner container 4 heated by a heater 3 and an outer shell 2 that accommodates the inner container 4. A gas introduction pipe 5 for introducing an atmospheric gas and an exhaust pipe 6 communicate with the inner container 4. A fluorine gas cylinder 16, an NH 3 gas cylinder 15, a NH 3 gas cylinder 15,
The N 2 gas cylinder 30 is connected. On the other hand, the exhaust pipe 6 has a vacuum pump 13 for exhausting gas in the inner container 4.
And an exhaust gas treatment device 14 are connected. In the figure, reference numeral 8 denotes a fan which is rotated by a motor 7 to stir the atmosphere gas in the inner container 4, and 11 denotes a basket made of wire mesh which fills the iron-based material 10.
【００２１】上記マッフル炉１内を２５０〜４５０℃に
昇温し、鉄系材料１０を装入してフッ素系ガスボンベ１
６からＮＦ3 等のフッ素系ガスを内容器４内に導入して
加熱保持してフッ化処理をし、ついで排気管６から内容
器４内のガスを真空ポンプ１３の作用で引出し、排ガス
処理装置１４内で無毒化して外部に放出する。つぎに、
ＮＨ3 ガスボンベ１５から内容器４内に窒化ガス（ＮＨ
3 ガス，ＮＨ3 ガス＋Ｎ2 ガス等）を導入し、３００〜
４５０℃に設定して加熱保持して窒化処理を行い、その
後、排気管６および排ガス処理装置１４を経由して内容
器４内のガスを外部に排出する。この一連の作業により
フッ化処理および窒化処理が行われる。The temperature inside the muffle furnace 1 is raised to 250 to 450 ° C., an iron-based material 10 is charged, and a fluorine-based gas cylinder 1 is charged.
6, a fluorine-based gas such as NF 3 is introduced into the inner container 4 and heated and held for fluorination treatment. Then, the gas in the inner container 4 is extracted from the exhaust pipe 6 by the action of the vacuum pump 13, and exhaust gas treatment is performed. It is detoxified in the device 14 and released to the outside. Next,
The nitriding gas (NH) is introduced into the inner container 4 from the NH 3 gas cylinder 15.
3 gas, NH 3 gas + N 2 gas, etc.)
The nitriding process is performed by setting the temperature to 450 ° C. and heating and holding, and then the gas in the inner container 4 is discharged to the outside via the exhaust pipe 6 and the exhaust gas treatment device 14. By this series of operations, the fluorination treatment and the nitridation treatment are performed.
【００２２】上記のように低温域で窒化処理することに
より、上記鉄系材料の表面層に、緻密で均一な厚み１〜
１０μｍの窒化物層が形成される。この窒化物層は、ε
−Ｆｅx Ｎ（２＜ｘ≦３：Ｎを７〜１１％という広範囲
の濃度で含む）の殆ど単相で構成されている。そして、
本発明の窒化処理によれば、窒化処理による鉄系材料の
寸法変化や面粗れがほとんど生じないのである。By performing the nitriding treatment at a low temperature range as described above, a dense and uniform thickness of 1 to
A 10 μm nitride layer is formed. This nitride layer
-Fe x N (2 <x ≦ 3: including a wide range of concentrations of N 7-11%) of which consists of almost single phase. And
According to the nitriding treatment of the present invention, dimensional changes and surface roughness of the iron-based material due to the nitriding treatment hardly occur.
【００２３】すなわち、従来の窒化処理では、ε−Ｆｅ
x Ｎおよびγ’−Ｆｅ4 Ｎという２種類の窒化物からな
る窒化物層が形成され、この窒化物層は、窒化処理条件
にもよるが、通常、１０〜３０μｍ程度の厚みになる。
そして、上記従来法で得られる窒化物層には「Ｎ」の濃
度勾配があり、表層部に「Ｎ」含有量の比較的多いε−
Ｆｅx Ｎ相が形成され、母材側に「Ｎ」含有量の比較的
少ないγ’−Ｆｅ4 Ｎ相が形成される。また、この窒化
物層には、断面の面積比率に換算して２０〜４０％にも
達する気孔（平均径０．３〜０．６μｍ）が数多く存在
する。そして、特にγ’−Ｆｅ4 Ｎでは気孔径が大きい
（γ’−Ｆｅ4 Ｎの解離圧が低いためと考えられる）。
しかも、上記従来の窒化物層は、ε−Ｆｅx Ｎは最表面
にごく薄く存在するだけで、全厚みの７０〜７５％は、
ε−Ｆｅx Ｎとγ’−Ｆｅ4 Ｎとが混在するか、γ’−
Ｆｅ4 Ｎだけからなっている。そして、γ’−Ｆｅ4 Ｎ
には粗大気孔が存在するため、上記従来の窒化方法で得
られた窒化物層には、粗大気孔を有するγ’−Ｆｅ4 Ｎ
が厚く形成されてしまい、製品の外形寸法が膨張して寸
法変化が生じたり、製品の面粗度や真円度等を悪化さ
せ、寸法精度を低下させる原因となる。このため、最終
加工仕上げが必要となって多大のコストがかかる。さら
に、圧縮機用部品のような高速摺動部材では、厳しい潤
滑環境下で高速摺動するため、上記のように窒化物層に
厚いγ’−Ｆｅ4 Ｎが形成されていると、γ’−Ｆｅ4
Ｎの粗大気孔の影響で面粗度の悪化をもたらし、ピッチ
ング摩耗を生じたり、摺動相手材を摩耗させたりし、耐
久性が悪くなる。That is, in the conventional nitriding treatment, ε-Fe
x N and gamma prime-Fe 4 nitrides of two kinds of nitride that N layer is formed, the nitride layer, depending on the nitriding condition, usually, the thickness of about 10 to 30 [mu] m.
The nitride layer obtained by the above-mentioned conventional method has a concentration gradient of “N”, and the surface layer has a relatively large “N” content of ε-
An Fe x N phase is formed, and a γ′-Fe 4 N phase having a relatively small “N” content is formed on the base material side. The nitride layer has many pores (average diameter: 0.3 to 0.6 μm) reaching 20 to 40% in terms of the area ratio of the cross section. In particular, γ′-Fe 4 N has a large pore diameter (presumably because the dissociation pressure of γ′-Fe 4 N is low).
Moreover, the conventional nitride layer, ε-Fe x N is only present very thinly on the outermost surface, 70 to 75% of the total thickness,
epsilon-Fe x N and gamma prime-Fe 4 or N and are mixed, Ganma'-
It consists only of Fe 4 N. And γ′-Fe 4 N
Has coarse atmospheric holes, the nitride layer obtained by the above-mentioned conventional nitriding method has γ′-Fe 4 N
Is formed thickly, and the outer dimensions of the product expand, causing dimensional changes, and the surface roughness and roundness of the product are deteriorated, resulting in a decrease in dimensional accuracy. For this reason, a final processing finish is required, and a large cost is required. Further, in a high-speed sliding member such as a compressor component, high-speed sliding is performed in a severe lubricating environment. Therefore, when a thick γ′-Fe 4 N is formed in the nitride layer as described above, γ ′ −Fe 4
The roughness of the surface is deteriorated by the influence of the coarse pores of N, causing pitting wear and abrading of a sliding partner material, resulting in poor durability.
【００２４】これに対し、本発明では、３００〜４５０
℃の低温域で窒化し、窒化物層の厚みを最大でも６μｍ
までとする。このようにすると、γ’−Ｆｅ4 Ｎが生成
せず、形成される窒化物層がε−Ｆｅx Ｎからなるもの
となる。なお、窒化物層の厚みが６μｍを越え厚くなる
に従って、γ’−Ｆｅ4 Ｎの量が大幅に増大する。そし
て、上記ε−Ｆｅx Ｎ相は、γ’−Ｆｅ4 Ｎ相と比較し
て気孔が極めて小さく、緻密である。このように、本発
明では、粗大気孔を有するγ’−Ｆｅ4 Ｎ相が生成せ
ず、ε−Ｆｅx Ｎからなる窒化物層が形成されるため、
寸法変化が非常に小さく、面粗度の劣化も少ない。On the other hand, in the present invention, 300 to 450
Nitriding at a low temperature of ℃, the maximum thickness of the nitride layer is 6μm
Up to. In this way, γ'-Fe 4 N is not generated, the nitride layer is formed becomes consisting ε-Fe x N. Note that, as the thickness of the nitride layer exceeds 6 μm, the amount of γ′-Fe 4 N greatly increases. The ε-Fe x N phase has extremely small pores and is dense as compared with the γ′-Fe 4 N phase. Thus, in the present invention does not generate the γ'-Fe 4 N phase with coarse pores, nitride layer is formed consisting of ε-Fe x N,
The dimensional change is very small, and the surface roughness is less deteriorated.
【００２５】上記のようにして得られた鉄系材料製品
は、圧縮機用部品のように、高速摺動部材として好適に
用いられる。すなわち、鉄系材料製品の表面に形成され
たε−Ｆｅx Ｎからなる窒化物層は、微細で緻密な気孔
の存在が、潤滑液を効果的に保持し、高速摺動において
も摩耗を最小限に抑えることができる。また、ε−Ｆｅ
x Ｎは、γ’−Ｆｅ4 Ｎのような粗大気孔がほとんどな
いため、窒化物層が破壊されてピッチング摩耗を生じた
り、摺動相手材を摩耗させたりすることがない。なお、
ε−Ｆｅx Ｎからなる窒化物層の厚みが１μｍ以上あれ
ば、上記のような潤滑効果が得られる。一方、１μｍ未
満では、窒化物層自体の厚みが薄いうえ、その直下に形
成される窒素拡散層も浅いため、表層部の硬度がそれほ
ど高くならず、充分な耐摩耗性が得られない。The iron-based material product obtained as described above is suitably used as a high-speed sliding member, such as a part for a compressor. Minimum i.e., nitride layer consisting of ε-Fe x N formed on the surface of the iron-based material products, the presence of fine and dense pores, lubricating liquid effectively retains the, the wear even at high sliding Can be minimized. Also, ε-Fe
x N, since coarse pores as γ'-Fe 4 N is little, or cause pitting wear nitride layer is destroyed, never or to wear the sliding counterpart material. In addition,
The thickness of the nitride layer consisting of ε-Fe x N is if more than 1 [mu] m, the lubricating effect as described above can be obtained. On the other hand, when the thickness is less than 1 μm, the thickness of the nitride layer itself is small and the nitrogen diffusion layer formed immediately below the nitride layer is also shallow.
【００２６】また、本発明の窒化処理方法では、４５０
℃以下という低温域で窒化処理するため、窒化雰囲気中
の〔Ｎ〕の浸透ポテンシャル（以下、「〔Ｎ〕ポテンシ
ャル」という）が極めて高くなる。これは、一般に鋼を
アンモニアガス中に保持したときの〔Ｎ〕ポテンシャル
は、下記の式（１）で表されるが、窒化温度が低温にな
るに従ってＮＨ3 の解離率が小さくなり、Ｈ2 濃度が低
くなるためである。このような低温における高い〔Ｎ〕
ポテンシャルの雰囲気下では、γ’−Ｆｅ4 Ｎよりもε
−Ｆｅx Ｎの方が核生成が容易である。一方、４５０℃
を越える高温では〔Ｎ〕ポテンシャルが小さくなり、ε
−Ｆｅx Ｎよりも熱力学的に安定なγ’−Ｆｅ4 Ｎの形
成が増大する。そして、一旦γ’−Ｆｅ4 Ｎが形成され
ると窒化物層全体の厚みは急激に増大してしまう。In the nitriding method of the present invention, 450
Since the nitriding treatment is performed in a low temperature range of not more than ℃, the penetration potential of [N] in the nitriding atmosphere (hereinafter referred to as “[N] potential”) becomes extremely high. This is because the [N] potential when steel is generally held in ammonia gas is expressed by the following equation (1). As the nitriding temperature becomes lower, the dissociation rate of NH 3 becomes smaller and H 2 becomes lower. This is because the concentration becomes low. High [N] at such low temperatures
Under a potential atmosphere, ε is larger than γ′-Fe 4 N.
Who -fe x N is easy nucleation. On the other hand, 450 ° C
[N] potential decreases at high temperatures exceeding
Formation of thermodynamically stable γ'-Fe 4 N is increased than -fe x N. Then, once γ′-Fe 4 N is formed, the thickness of the entire nitride layer rapidly increases.
【００２７】[0027]
【化１】ｐＮＨ3 ／ｐＨ2 3/2 …（１） ｐＮＨ3 ：ＮＨ3 の分圧 ｐＨ2 ：Ｈ2 の分圧[Formula 1] pNH 3 / pH 2 3/2 ... (1) Partial pressure of pNH 3 : NH 3 Partial pressure of pH 2 : H 2
【００２８】また、本発明の窒化処理方法では、材料中
に炭素が多く存在する鉄系材料を使用することが好まし
い。すなわち、ε−Ｆｅx Ｎは、炭素を多量に固溶する
ため、炭素が多く存在する鉄系材料を使用した場合に、
より安定的に核生成し成長するからである。したがっ
て、鋳鉄や浸炭処理品等の炭素の多い材料では、γ’−
Ｆｅ4 Ｎは核生成が起こり難く、ε−Ｆｅx Ｎからなる
窒化物層が形成されるのである。例えば、ＦＣＤ６００
（球状黒鉛鋳鉄）では、窒化物層全体の厚みが６μｍ程
度になるまでγ’−Ｆｅ4 Ｎは形成されない。一方、Ｓ
ＣＭ４３５のような中炭素鋼では、窒化物層全体の厚み
が２〜３μｍ程度になると、その窒化物層中にγ’−Ｆ
ｅ4 Ｎが形成されてしまう。In the nitriding method of the present invention, it is preferable to use an iron-based material in which a large amount of carbon is present in the material. That, ε-Fe x N, since a large amount dissolved carbon, in the case of using a ferrous material present many carbon,
This is because nucleation and growth occur more stably. Therefore, in materials with high carbon such as cast iron and carburized products, γ'-
Fe 4 N is the hardly occurs nucleation, nitride layer consisting of ε-Fe x N is formed. For example, FCD600
In (spheroidal graphite cast iron), γ′-Fe 4 N is not formed until the thickness of the entire nitride layer becomes about 6 μm. On the other hand, S
In a medium carbon steel such as CM435, when the thickness of the entire nitride layer becomes about 2 to 3 μm, γ′-F
e 4 N is formed.
【００２９】特に、上記鉄系材料として鋳鉄を使用する
ことが好ましい。すなわち、鋳鉄は、鋳造によって複雑
形状品が容易に得られ、析出黒鉛による摺動性や、振動
減衰特性も良く、耐食性にも優れるうえに安価である等
の種々の優れた特性を有し、摺動部材として極めて良好
な材料である。ところが、鋳鉄は、鋳造時の残留応力が
大きいために熱変形も大きいうえ、応力除去焼鈍等を施
したとしても２次黒鉛の析出による膨張等の問題がある
ため、窒化処理によって高精度のものを得ることができ
なかった。しかも、鋳鉄は、Ｓｉを多量に含有するた
め、窒化処理自体が困難で、特に低温窒化は不可能であ
った。本発明では、窒化に先立ち、フッ化処理すること
により、鋳鉄の表面を〔Ｎ〕原子の浸透が容易な状態と
し、４５０℃以下の比較的低温での窒化処理を可能にし
たのである。In particular, it is preferable to use cast iron as the iron-based material. In other words, cast iron has various excellent properties such as easy formation of a complex-shaped product by casting, slidability by precipitated graphite, good vibration damping properties, excellent corrosion resistance and low cost. It is a very good material for a sliding member. However, cast iron has high thermal deformation due to large residual stress during casting, and even if subjected to stress relief annealing etc., it has problems such as expansion due to precipitation of secondary graphite. Could not get. Moreover, since cast iron contains a large amount of Si, nitriding treatment itself is difficult, and low-temperature nitriding in particular has been impossible. According to the present invention, the surface of the cast iron is easily permeable to [N] atoms by performing fluorination treatment prior to nitriding, and nitriding treatment at a relatively low temperature of 450 ° C. or less is enabled.
【００３０】つぎに、実施例について比較例と併せて説
明する。Next, examples will be described together with comparative examples.
【００３１】[0031]
【実施例】球状黒鉛鋳鉄（ＦＣＤ６００）を鋳込み成形
したのち切削加工し、図２に示すように、円柱状のシャ
フト部２と、中央よりやや端部寄りに設けられたクラン
ク部３とからなるクランクシャフト１を形成した。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A spheroidal graphite cast iron (FCD600) is cast, molded and then cut, as shown in FIG. 2, comprising a cylindrical shaft portion 2 and a crank portion 3 provided slightly closer to the end than the center. The crankshaft 1 was formed.
【００３２】このクランクシャフトを、図１に示すマッ
フル炉に装入し、Ｎ2 ガス雰囲気下で昇温し、３５０℃
に達したのちＮ2 ＋１０体積％ＮＦ3 ガス雰囲気下で３
５０℃×２０分間フッ化処理した。つぎに、ＮＨ3 ガス
を導入し、４００℃まで昇温し、１００体積％ＮＨ3 ガ
ス雰囲気下で４００℃×６時間窒化処理し、本発明の鉄
系材料製品を得た。This crankshaft was charged into the muffle furnace shown in FIG. 1 and heated in an N 2 gas atmosphere at 350 ° C.
After reaching 3 % in an N 2 + 10% by volume NF 3 gas atmosphere.
Fluorination treatment was performed at 50 ° C. for 20 minutes. Next, an NH 3 gas was introduced, the temperature was raised to 400 ° C., and nitriding was performed at 400 ° C. for 6 hours in a 100% by volume NH 3 gas atmosphere to obtain an iron-based material product of the present invention.
【００３３】[0033]
【比較例】上記実施例と同様に形成したクランクシャフ
トを、７０体積％ＮＨ3 ガス＋３０体積％ＲＸガス雰囲
気下で５７０℃×２時間窒化処理し、鋳鉄系材料製品を
得た。Comparative Example A crankshaft formed in the same manner as in the above example was nitrided at 570 ° C. for 2 hours in an atmosphere of 70% by volume NH 3 gas + 30% by volume RX gas to obtain a cast iron material product.
【００３４】上記各実施例および比較例のクランクシャ
フトの断面金属顕微鏡写真をそれぞれ図３および図４に
示す。実施例では、約２μｍの窒化物層が形成されてい
る。これに対し、比較例では、約１２μｍの窒化物層が
形成されていることがわかる。また、各クランクシャフ
トの断面電子顕微鏡写真を図５および図６に示す。実施
例では、窒化物層は緻密で気孔がほとんど見られない。
これに対し、比較例では、多数の粗大気孔が存在してい
るのがわかる。FIGS. 3 and 4 show cross-sectional metal micrographs of the crankshafts of the above Examples and Comparative Examples, respectively. In the embodiment, a nitride layer of about 2 μm is formed. On the other hand, in the comparative example, it can be seen that a nitride layer of about 12 μm was formed. 5 and 6 show cross-sectional electron micrographs of each crankshaft. In the example, the nitride layer is dense and has almost no pores.
On the other hand, in the comparative example, it can be seen that a large number of coarse pores exist.
【００３５】また、上記各クランクシャフトの表面をＸ
線回折した結果を図７および図８に示す。実施例では、
ε−Ｆｅ3 Ｎの大きなピークが明瞭に見られ、γ’−Ｆ
ｅ4Ｎのピークはほとんど見られない。これに対し、比
較例では、γ’−Ｆｅ4 Ｎの大きなピークが明瞭に見ら
れ、ε−Ｆｅ3 Ｎのピークは非常に弱いのがわかる。ま
た、実施例のε−Ｆｅ3 Ｎのピークは、回折線が比較例
よりブロードであり、半値幅（ピーク全高の半分の高さ
におけるピーク幅）が広く、結晶が微細であることを物
語っている。The surface of each of the above crankshafts is represented by X
The results of the line diffraction are shown in FIGS. In the example,
A large peak of ε-Fe 3 N is clearly seen, and γ′-F
Almost no e 4 N peak is seen. On the other hand, in the comparative example, a large peak of γ′-Fe 4 N is clearly seen, and the peak of ε-Fe 3 N is very weak. The peak of ε-Fe 3 N in the examples indicates that the diffraction line is broader than the comparative example, the half width (peak width at half the height of the peak) is wide, and the crystal is fine. I have.
【００３６】さらに、上記各クランクシャフトの表面硬
度と、軸振れ，表面の面粗度，外形寸法の膨れの測定結
果を下記の表１に示す。なお、面粗度は、ミツトヨ社製
ＲＡ−１００、外形寸法および軸振れは、ミツトヨ社製
ダイヤルゲージを用いて測定を行った。Table 1 below shows the results of measurement of the surface hardness, shaft runout, surface roughness, and external dimensions of each of the crankshafts. In addition, the surface roughness was measured using RA-100 manufactured by Mitutoyo Corporation, and the external dimensions and shaft runout were measured using a dial gauge manufactured by Mitutoyo Corporation.
【００３７】[0037]
【表１】 [Table 1]
【００３８】上記表１からわかるとおり、実施例では、
比較例に比べて表面硬度がやや高く、真円度，面粗度，
外形寸法膨れ、いずれも比較例よりも良好な値を示し、
高精度が得られていることがわかる。As can be seen from Table 1 above, in the embodiment,
The surface hardness is slightly higher than the comparative example, and the roundness, surface roughness,
Dimensional swelling, both show better values than the comparative example,
It can be seen that high accuracy has been obtained.
【００３９】[0039]
【発明の効果】以上のように、本発明の窒化処理方法に
よれば、窒化処理に先立って、フッ素系ガス雰囲気下で
鉄系材料を加熱保持してフッ化処理するため、３００〜
４５０℃の低温域での窒化処理が可能となる。このた
め、残留応力解放や再結晶等による熱変形が軽減され
る。さらに、上記低温域での窒化処理により、表層部の
少なくとも一部に、厚み１〜１０μｍの窒化物層を形成
するため、処理前後の寸法変化や歪みが極めて少なくな
り、寸法精度，面粗度等に優れた製品が得られる。した
がって、製品を高精度に保つことができ、研削仕上げ等
の仕上げ加工が不要になり、コストを低減することがで
きる。As described above, according to the nitriding method of the present invention, prior to the nitriding treatment, the iron-based material is heated and held in a fluorine-based gas atmosphere to perform the fluorination treatment.
Nitriding at a low temperature of 450 ° C. becomes possible. Therefore, thermal deformation due to release of residual stress or recrystallization is reduced. Further, since a nitride layer having a thickness of 1 to 10 μm is formed on at least a part of the surface layer portion by the nitriding treatment in the low temperature range, dimensional change and distortion before and after the treatment are extremely reduced, and dimensional accuracy and surface roughness are reduced. Excellent products are obtained. Therefore, the product can be maintained with high precision, finishing work such as grinding finish is not required, and cost can be reduced.
【図１】本発明の窒化処理方法に用いる炉の構成図であ
る。FIG. 1 is a configuration diagram of a furnace used for a nitriding treatment method of the present invention.
【図２】本発明の高速摺動部材（クランクシャフト）を
示す図であり、（ａ）は正面図、（ｂ）は右側面図、
（ｃ）は背面図である。FIG. 2 is a view showing a high-speed sliding member (crankshaft) of the present invention, wherein (a) is a front view, (b) is a right side view,
(C) is a rear view.
【図３】実施例の高速摺動部材の表層部の金属組織を示
す金属顕微鏡写真である。FIG. 3 is a metal micrograph showing a metal structure of a surface layer portion of a high-speed sliding member of an example.
【図４】比較例の表層部の金属組織を示す金属顕微鏡写
真である。FIG. 4 is a metal micrograph showing a metal structure of a surface portion of a comparative example.
【図５】実施例の高速摺動部材の表層部の金属組織を示
す電子顕微鏡写真である。FIG. 5 is an electron micrograph showing a metal structure of a surface layer portion of the high-speed sliding member of the example.
【図６】比較例の表層部の金属組織を示す電子顕微鏡写
真である。FIG. 6 is an electron micrograph showing the metal structure of the surface layer of the comparative example.
【図７】実施例の高速摺動部材のＸ線回折結果を示す線
図である。FIG. 7 is a diagram showing an X-ray diffraction result of the high-speed sliding member of the example.
【図８】比較例のＸ線回折結果を示す線図である。FIG. 8 is a diagram showing an X-ray diffraction result of a comparative example.
Claims (7)
気下で鉄系材料を加熱保持してフッ化処理し、ついで、
窒化処理の際の温度を３００〜４５０℃に設定し、上記
フッ化処理済の鉄系材料を窒化処理することにより、上
記フッ化処理済の鉄系材料の表層部の少なくとも一部
に、厚み１〜１０μｍの窒化物層を形成することを特徴
とする鉄系材料の窒化処理方法。1. Prior to the nitriding treatment, an iron-based material is heated and held in a fluorine-based gas atmosphere to perform a fluoridation treatment.
By setting the temperature at the time of the nitriding treatment to 300 to 450 ° C. and nitriding the fluorinated iron-based material, at least a part of the surface layer of the fluorinated iron-based material has a thickness. A method for nitriding an iron-based material, comprising forming a nitride layer having a thickness of 1 to 10 μm.
る請求項１または２記載の鉄系材料の窒化処理方法。2. A nitride layer formed is ε-Fe x N claim 1 or 2, nitriding processing method of an iron based material according.
記載の鉄系材料の窒化処理方法。3. The method according to claim 1, wherein the iron-based material is cast iron.
A method for nitriding a ferrous material as described in the above.
くとも一部に、厚み１〜１０μｍの窒化物層が形成され
ていることを特徴とする鉄系材料製品。4. An iron-based material product, wherein the base material is made of an iron-based material, and a nitride layer having a thickness of 1 to 10 μm is formed on at least a part of a surface layer portion.
記載の鉄系材料製品。5. A method according to claim 4 nitride layer is ε-Fe x N
The iron-based material product described.
５記載の鉄系材料製品。6. The iron-based material product according to claim 4, wherein the iron-based material is cast iron.
る請求項４〜６のいずれか一項に記載の鉄系材料製品。7. The ferrous material product according to claim 4, which is used as a high-speed sliding member.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9067378A JP3023322B2 (en) | 1997-03-04 | 1997-03-04 | Iron-based material nitriding method and iron-based material product obtained thereby |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9067378A JP3023322B2 (en) | 1997-03-04 | 1997-03-04 | Iron-based material nitriding method and iron-based material product obtained thereby |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10245668A true JPH10245668A (en) | 1998-09-14 |
| JP3023322B2 JP3023322B2 (en) | 2000-03-21 |
Family
ID=13343300
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9067378A Expired - Fee Related JP3023322B2 (en) | 1997-03-04 | 1997-03-04 | Iron-based material nitriding method and iron-based material product obtained thereby |
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| Country | Link |
|---|---|
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004081252A1 (en) * | 2003-03-10 | 2004-09-23 | Kabushiki Kaisha Riken | Nitrided valve lifter and method for manufacture thereof |
| JP2007031770A (en) * | 2005-07-26 | 2007-02-08 | Honda Motor Co Ltd | Steel-made spring member |
| JP2013095966A (en) * | 2011-11-01 | 2013-05-20 | Panasonic Corp | Sliding member, surface treatment method of the same, and bearing apparatus and compressor using the same |
| JP2016023353A (en) * | 2014-07-23 | 2016-02-08 | 日立建機株式会社 | Slide structure and production method for the same |
-
1997
- 1997-03-04 JP JP9067378A patent/JP3023322B2/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004081252A1 (en) * | 2003-03-10 | 2004-09-23 | Kabushiki Kaisha Riken | Nitrided valve lifter and method for manufacture thereof |
| JP2007031770A (en) * | 2005-07-26 | 2007-02-08 | Honda Motor Co Ltd | Steel-made spring member |
| JP2013095966A (en) * | 2011-11-01 | 2013-05-20 | Panasonic Corp | Sliding member, surface treatment method of the same, and bearing apparatus and compressor using the same |
| JP2016023353A (en) * | 2014-07-23 | 2016-02-08 | 日立建機株式会社 | Slide structure and production method for the same |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3023322B2 (en) | 2000-03-21 |
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